Method for manufacturing electroluminescence device

ABSTRACT

A manufacturing method of an electroluminescence element of is provided, which causes a light emitting layer to emit light by applying a desired voltage between an anode and a cathode, with the light emitting layer in between, and obtains visible rays by wavelength-converting the emitted light using color changing media formed in individual pixel regions. The method consists of forming a partitioning member having openings corresponding to the pixel regions on a substrate, discharging color changing media precursors into the openings using a liquid drop discharge head, and forming the color changing media by solidifying the color changing media precursors discharged onto the substrate. With this method, it is possible to discharge the color changing media precursors while adjusting the doping ratio of color changing constituents of the color changing media precursors on the spot, thus making it easier to adjust color of the color changing media.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a manufacturing method of anelectroluminescence (EL) element. More particularly, the inventionrelates to a manufacturing technique of an EL element of forming colorchanging media (CCM) without using a lithographic process.

2. Description of Related Art

An EL element is an organic EL element or an inorganic EL element. Theorganic EL element is a self-emitting type element emitting light byelectrically exciting a fluorescent organic compound. This element ischaracterized by a high luminance, a high-speed response, a high viewingangle, face emission, and a thin thickness, and this element can emitlight in multiple colors. Further, this element has a feature that it isa fully solid element emitting light through DC impression of a lowvoltage of a few volts, and fluctuation of properties is slight at lowtemperature. Since the EL element using an organic substance as a lightemitting material can easily cover the entire visible range throughadoption of a structure which may consist of a combination of a lightemitting layer and color changing media and selection of a materialforming the light emitting layer and color changing media, efforts areactively made for application to a full-color flat panel display. Knownmethods for full-color application of the EL element include, forexample, a method of color-changing a white emission (the whiteemission/color changing method) and a method of color-changing a blueemission (the blue emission/color changing method).

When manufacturing a structure adopting the white emission/colorchanging method or the blue emission/color changing method forfull-color application of the EL element, however, it is theconventional practice to form color changing media, and to performpatterning via a lithographic process into a shape corresponding topixel regions. Formation of the color changing media on a substrate byusing the lithographic process causes much waste of the color changingmedia material, leading to a higher manufacturing cost. The necessity ofphotosensitivity for the color changing media material results in asmaller range of material selection. Further problems include a highrunning cost of facilities necessary for the lithographic process and alarger equipment space.

The EL element is expected to be applicable to full-color flat paneldisplays in the future, as shown in FIG. 6, and the reduction of themanufacturing cost is an indispensable prerequisite.

SUMMARY OF THE INVENTION

The present invention was developed in view of the aforementionedproblems and has an object to provide a method of manufacturing anelectroluminescence element which may consist of a light emitting layerand color changing media for manufacturing color changing media withoutusing a lithographic process, and to provide a high-performanceelectroluminescence element manufacture by this method.

A first manufacturing method of an electroluminescence element of thepresent invention may consist of the steps of causing a light emittinglayer to emit light by applying a desired voltage between an anode and acathode, with the light emitting layer in between, and obtaining visiblerays by wavelength-converting the emitted light using color changingmedia formed in individual pixel regions. This method may furtherconsist of a first step of forming partitioning members having openingscorresponding to the pixel regions on a substrate, a second step ofdischarging a color changing media precursor into the openings using aliquid discharge head, and a third step of forming color changing mediaby solidifying the color changing media precursor discharged onto thesubstrate.

Particularly, in the above-mentioned first method, the second stepshould preferably be a step of discharging the color changing mediawhile adjusting the doping ratio of color changing constituents of thecolor changing media.

The color changing media precursor is a precursor of color changingmedia selected from the group consisting of red color changing media,green color changing media and blue color changing media. In this case,the precursor of the red color changing media should preferably have achemical composition which may consist of any one of a cyanine-basedpigment, a pyridine-based pigment, a xanthene-based pigment and anoxadine-based pigment.

The precursor of the red color changing media may adopt a chemicalcomposition prepared by dispersing: (a) a rhodamine-based fluorescentpigment, and (b) a fluorescent pigment, which absorbs rays in the blueregion and induces energy transfer or re-absorption to therhodamine-based fluorescent pigment, into a light transmitting medium.The precursor of the green color changing media may have a chemicalcomposition which may consist of, for example, a stilbene-based compoundand a coumarin-based compound. The precursor of the blue color changingmedia may have a chemical composition which may consist of, for example,a coumarin pigment.

In the aforementioned first method, a light emitting layer shouldpreferably be formed by coating or by vapor deposition so as to form anupper layer relative to the color changing media after theabove-mentioned process of forming the color changing media (the thirdstep).

A second manufacturing method of an electroluminescence element of theinvention may consist of the steps of causing a light emitting layer toemit light by applying a desired voltage between an anode and a cathodewith the light emitting layer in between, and obtaining visible rays bywavelength-converting the emitted light using color changing mediaformed in individual pixel regions. This method may further consist of afirst step of forming anodes at positions corresponding to the pixelregions on a substrate, a second step of forming partitioning memberswhich partition between the anodes, and have openings at positionscorresponding to the pixel regions, a third step of discharging aprecursor of the color changing media into the openings using a liquiddrop discharge head, and filling the anodes with the precursor of thecolor changing media, and a fourth step of forming the color changingmedia by solidifying the precursor of the color changing media.

Particularly, in the above-mentioned second method, the third stepshould preferably be a step of discharging the precursor of the colorchanging media while adjusting the doping ratio of color changingconstituents of the precursor of the color changing media.

The precursor of the color changing media is conductive and is aprecursor of color changing media selected from a group consisting ofred color changing media, green color changing media and blue colorchanging media.

In the aforementioned second method, a light emitting layer shouldpreferably be formed by coating or by vapor deposition so as to form anupper layer relative to the color changing media after theabove-mentioned process of forming the color changing media (the fourthstep).

The contact angle between a material composing a nozzle surface of theliquid drop discharge head and the precursor of the color changing mediashould preferably be within a range from 30 to 170 deg. The precursor ofthe color changing media should preferably have a viscosity within arange from 1 to 20 mPas. Further, the precursor of the color changingmedia should preferably have a surface tension within a range from 20 to70 dynes/cm. The liquid drop discharge head should preferably comprise apressurizing chamber substrate having a pressurizing chamber whichstores the color changing media precursor and a piezo-electric thin filmelement attached to a position permitting application of a pressure tothe pressurizing chamber.

Further, according to the invention, the electroluminescence element forcausing a light emitting layer to emit light by applying a desiredvoltage between an anode and a cathode arranged with the light emittinglayer in between, and obtaining visible rays by wavelength-convertingthe emitted light with color changing media formed for each of pixelregions, may consist of the color changing media between the anode andthe cathode. The electroluminescence element has, for example, alamination structure comprising a cathode, a light emitting layer, colorchanging media and an anode. Particularly, the color changing media isconductive and is color changing media selected from the groupconsisting of red color changing media, green color changing media andblue color changing media.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(A)-(C) are sectional views illustrating the manufacturing methodof the EL element of first embodiment of the present invention in asequence of steps;

FIGS. 2(A)-3(F) are sectional views illustrating the manufacturingmethod of the EL element of second embodiment of the invention in asequence of steps;

FIG. 4 is a sectional view illustrating the manufacturing method of theEL element of the third embodiment of the invention in a sequence ofsteps;

FIG. 5 is a sectional view illustrating the manufacturing method of theEL element of fourth embodiment of the invention in a sequence of steps;and

FIG. 6 is a diagram of an exemplary display used in accordance with theclaimed invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will now be described withreference to the drawings.

First Embodiment

The structure of the EL element and the manufacturing method thereof ofthe first embodiment will be described with reference to FIGS. 1(A)-(C).

FIG. 1(C) illustrates the structure of the EL element of the blueemission/color changing type. Red color changing media 40A, green colorchanging media 40B, and blue color changing media 40C are formed on asubstrate 10, and covered with a light-transmissive protection film 90.Anodes 30 made of ITO (indium thin oxide) are formed at positionscorresponding to the color changing media 40A to 40C are formed on theprotecting film 90. A blue light from recombination of electrons andholes in a light emitting layer 50 by applying a DC voltage between ananode 30 and a cathode 60 can be obtained. R, G and B light sources orimages are obtained by converting the blue light into red (R), green (G)and blue (B) by means of the color changing media 40A to 40C.

When blue emission of the light emitting layer 50 sufficiently satisfiesthe demand, the blue color changing media 40C is not necessary.

(Manufacturing Process of EL Element)

The manufacturing process of the EL element of this embodiment will nowbe described with reference to FIGS. 1(A)-(C).

Color Changing Media Precursor Discharge Process (FIG. 1(A))

This is a process of discharging the color changing media precursor ontothe glass substrate 10. As the glass substrate 10, for example, a flattransparent glass substrate having a size of about 300 mm×300 mm×0.7 mmis prepared. This transparent glass substrate should preferablywithstand a heat of 350° C., be resistant to chemicals such as acids andalkalies, and be capable of being mass-produced.

A partitioning member (bank) 20 is first formed on the glass substrate10 to facilitate forming color changing media at a desired position in adesired shape on the glass substrate 10. The partitioning member 20 hasa shape provided with an opening corresponding to a pixel region. Thematerial for this partitioning member 20 is an acrylic resin or apolyimide resin. The partitioning member 20 has a height within a rangeof from 0.5 to 2 mm, which can be adjusted as required. It isrecommendable to blend a fluororesin or a fluorine-based surfactant withthis partitioning member 20 or plasma-treat the partitioning member 20with CF₄. This reduces wettability with ink, thus permitting preventionof ink mixing on the partitioning member 20.

The color changing media precursor is supplied to the openings betweenthe partitioning members 20 through discharge. Discharge of the colorchanging media precursor is accomplished by means of a liquid dropdischarge head 2. The liquid drop discharge head 2 may be of thepiezo-jet type or of a type of discharging by the use of production ofbubbles caused by generation of heat. In the piezo-jet type, the head 2has a pressurizing chamber substrate having a pressurizing chamber whichmay consist of a nozzle plate and a piezo thin film element. By drivingthe piezo thin film element, a fluid (the color changing media precursorin this case) filling the pressurizing chamber is pressurized in amoment and discharged through the nozzle selectively into a prescribedregion. In the type of discharging which uses the production of bubblescaused by heat generation, the head 2 has a heater is provided in thepressurizing chamber communicating with the nozzle. The fluid near thenozzle is brought to a boil by increasing temperature of this heater,and the fluid is discharged under the effect of volumetric expansion bybubbles produced at this point. The piezo jet type is preferable becausethere is no change in the color changing media precursor caused byheating.

First, as shown in FIGS. 1(A)-(C), the red color changing mediaprecursor 40 a is discharged at a position corresponding to the pixelregion (region corresponding to red pixels) on the substrate 10. Amaterial containing (a) a rhodamine-based fluorescent pigment, and (b) afluorescent pigment which absorbs the blue region, and induces energytransfer or re-absorption to the rhodamine-based fluorescent pigment, isused as the red color changing media precursor.

The fluorescent pigment should preferably be capable of absorbing bluerays of up to 520 nm, and have absorbability of at least OD 1.0 for arange of from 420 to 490 nm. The rhodamine-based fluorescent pigmentshould preferably contain a naphthalimide fluorescent pigment or acoumarin-based fluorescent pigment. With this chemical composition, itis possible to change an emitted color of the blue emitting layer intored at a high efficiency of at least 33%.

Then, the precursor 40 b of the green color changing media is dischargedto a position corresponding to the pixel region (region corresponding togreen pixels) on the substrate 10. The precursor 40 b of the green colorchanging media should preferably contain a pigment of a stilbene-basedcompound or a coumarin-based compound.

As required, the precursor 40 c of the blue color changing media isdischarged to a position corresponding to the pixel region on thesubstrate 10. The precursor 40 c of the blue color changing media shouldpreferably contain a coumarin-based pigment. When the colored light(blue) of the emitting layer 50 sufficiently satisfies the demand, thisprocess is not necessary.

According to the above-mentioned method, it is possible to discharge theprecursors of the color changing media while adjusting the doping ratioof the color changing constituents of the color changing media, thusmaking it easier to perform color coordination.

Physical properties (contact angle, viscosity and surface tension) ofthese color changing media precursors should preferably have thefollowing values.

(1) Contact Angle

The contact angle between the material composing the nozzle surface ofthe liquid drop discharge head and the color changing media precursorshould preferably be set within a range of from 30 to 170 deg. Thecontact angle can be adjusted by appropriately increasing or decreasingthe amount of water, NMP, DMI, ethanol, or diethyleneglycol, and shouldpreferably be set particularly within a range of from 35 to 65 deg.

When the color changing media precursor has a contact angle within thisrange relative to the nozzle surface of the discharge head, it ispossible to inhibit occurrence of a flight bend upon discharging, thuspermitting accurate discharge control. With a contact angle of under 30deg, the color changing media precursor has an increased wettability onthe nozzle surface, and upon discharging the color changing mediaprecursor, the precursor may asymmetrically adhere around the nozzlehole. An attraction force acts between the color changing mediaprecursor adhering to the nozzle hole and the color changing mediaprecursor discharged. As a result, the color changing media precursor isdischarged under a non-uniform force, resulting in occurrence of aflight bend, and this may make it impossible to hit the target position.This leads to a high flight bend frequency. With a contact angle of over170 deg, on the other hand, interaction between the color changing mediaprecursor and the nozzle hole becomes minimum, leading to an unstableshape of meniscus at the nozzle tip. It may become consequentlydifficult to control the amount of discharge of the color changing mediaprecursor and the discharge timing.

The term “flight bend” as used in the invention means occurrence of ashift of the hitting position of the color changing media precursor oflarger than 30 mm from the target position when discharging the colorchanging media precursor through the nozzle hole. The flight bendfrequency means the time before occurrence of a flight bend whencontinuously discharging the same at an oscillation frequency of, forexample, 14.4 kHz of the piezo thin film element of the liquid dropdischarge head.

(2) Viscosity

The color changing media precursor should preferably have a viscositywithin a range of from 1 to 20 mPas. The viscosity can be adjusted byappropriately changing the amount of glycerine or ethylene glycol, andshould preferably be particularly within a range of from 2 to 4 mPas.

With a viscosity of the color changing media precursor of under 1 mPa,the meniscus of the color changing media at the nozzle hole is notstable, and this may make it difficult to perform discharge control ofthe precursor. With a viscosity of over 20 mPas, on the other hand, thecolor changing media precursor cannot be smoothly discharged from thenozzle hole, and discharge of the color changing media precursor becomesdifficult unless specifications for the liquid drop discharge head aremodified, for example, to enlarge the nozzle hole. Further, with a highviscosity, solid constituents of the color changing media precursor areeasily precipitated, resulting in a higher frequency of nozzle holeclogging.

(3) Surface Tension

The surface tension of the color changing media precursor shouldpreferably be set within a range of from 20 to 70 dyne/cm. The surfacetension can be adjusted by appropriately changing the amount of water,NMP, DMI, ethanol, diethyleneglycol, glycerine, xylene, tetralyne or amixture of these solvents, and should preferably be set particularlywithin a range of from 25 to 60 dyne/cm.

By setting the surface tension within the above-mentioned range, it ispossible to inhibit occurrence of a flight bend and reduce the flightbend frequency, as in the aforementioned case of the contact angle. Witha surface tension of over 70 dyne/cm, the shape of meniscus at thenozzle tip is not stable, and this may make it difficult to performcontrol of the amount of discharge of the color changing media and thedischarge timing. With a surface tension of under 20 dyne/cm, the colorchanging media precursor has an increased wettability to the materialforming the nozzle surface, and this may result in occurrence of aflight bend and a higher flight bend frequency as in the above-mentionedcase of contact angle.

The flight bend occurs mainly when wettability of the nozzle hole isnon-uniform, or when clogging is caused by adhesion of solidconstituents of the color changing media precursor, and can beeliminated by cleaning the liquid drop discharge head (hereinafterreferred to as “flashing”). Flashing is usually to impart such afunction to the liquid drop discharge head mechanism to prevent cloggingor flight bend by modifying the liquid drop discharge head mechanism,and designed to forcedly discharge a prescribed amount of color changingmedia precursor when discharge of the color changing media precursor isdiscontinued for a certain period of time (hereinafter referred to asthe “flashing time”). The flashing time means a period of time from themoment when the nozzle not discharging the color changing mediaprecursor dries up to the occurrence of a flight bend, and servestherefore as an indicator showing properties of the color changingmedia. A longer flashing time is more suitable for the ink jet printingtechnique, and permits stable discharge of the color changing mediaprecursor for a long period of time.

Therefore, when the color changing media precursor has theabove-mentioned values of physical properties, it is possible to extendthe flashing time and to maintain a fresh state of the interface betweenthe open air and the color changing media precursor. Because the densityof dots of the discharged color changing media precursor can be keptuniform irrespective of the discharge time point, it is possible toprevent the occurrence of color blurs of the color changing media.Further, an excellent straight flight property upon discharge of theprecursor makes it easier to perform control of the liquid dropdischarge head, and adopt a simpler structure of the manufacturingequipment.

The aforementioned ranges of physical properties are preferable rangesunder a temperature condition of 20° C.

After supplying the color changing media precursor selectively onto thesubstrate 10 by discharging, the color changing media precursor issolidified through a heat treatment. The solvent constituents areevaporated by this process, giving color changing media 40A, 40B and40C.

Process Forming Protecting Film and Anode (FIG. 1(B))

This is a process of forming a protecting film 90 and an anode 30 on thesubstrate 10.

The protecting film 90 is formed from a light-transmissive material,such as an acrylic resin by a film forming method, such as the spin coatmethod, the bar coat method, the printing method or the ink jet method.The film has a thickness of 2 mm. Then, an anode 30 is formed on thesurface of the protecting film 90. A light-transmissive conductivematerial such as ITO, or a composite oxide of indium oxide and zincoxide is used for forming the anode. Among others, ITO has a large workfunction, and the hole serves as a positive pole for injection in to theblue emitting layer, thus having properties preferable as an anode. Inthis process, ITO is formed into a film having a thickness of 0.15 mm bysputtering, and patterned into a shape corresponding to the colorchanging media 40A to 40C.

Process Forming Blue Emitting Layer and Cathode (FIG. 1(C))

This is a process of forming a blue emitting layer 50, and a cathode 60on the protecting film 90, so as to cover the anode 30. As lightemitting materials for an organic EL element, there are available apigment molecule which is a low molecule and a conductive polymer whichis a conjugated polymer. A low molecular material is used for forming anorganic thin film mainly by vapor deposition, and a polymer-basedmaterial, by the spin coat method. Although not shown in FIGS. 1(A)-(C),a double-hetero structure may be built by forming a hole transfer layerand an electron transfer layer with the blue emitting layer 50 inbetween.

More specifically, the film forming process is as follows. First, 200 mg4-4′bis (N-phenyl-N(3-methylphenyl)amino) biphenol (TPD) are put in aresistance-heating board made of molybdenum, 200 mg 4-4′bis(2,2-diphenylvinyl) biphenyl (DPVBi) and tris (8-quinolinol) aluminum(Alg) are put in another resistance-heating board made of molybdenum,and the interior of a vacuum chamber is pressure-reduced. The boardcontaining TPD is heated to a temperature of 215 to 220° C. to depositTPD onto the substrate at a vapor depositing rate within a range of from0.1 to 0.3 nm/s, and thus to form a hole transfer layer having athickness of 60 nm. At this point, the substrate is at the roomtemperature. Then, DPVBi is deposited under conditions including a boardtemperature of 250° C. and a vapor depositing rate of from 0.1 to 0.2nm/s to form a blue emitting layer 50 having a thickness of 40 nm. Then,Alg is further deposited under conditions including a board temperatureof 250° C. and a vapor depositing rate of from 0.1 to 0.3 nm/s to forman electron transfer layer having thickness of 20 nm.

Other applicable materials for the blue emitting layer 50 includepigment molecules of anthracene, Zn(OXZ)₂, PPCP, distilbenzene (DSB),and derivatives thereof (PESB). These materials can be formed into afilm by the organic molecular beam deposition (OMDB) method. Accordingto this method, it is possible to control the film thickness to amolecular order. The material for the blue emitting layer 50 is notlimited to an organic thin film, but it may be a thin film made of aninorganic material, such as strontium sulfide added with cerium. Theinorganic thin film should preferably have a high insulation pressureresistance, an emitting center having an appropriate emission color, andbe free from impurities or defects impairing emission.

Then, a cathode 60 is formed on the blue emitting layer 50. Preferablematerials for the cathode include ones having a small work function,particularly alkaline metals and alkali earth metals. Among others, forexample, alloys such as Mg/Ag and Al/Li are suitable. More specifically,the film is formed as follows. First, 0.5 g silver wire are put in atungsten basket, and 1 g magnesium ribbon is put in a board made ofmolybdenum. Pressure in a vacuum chamber is reduced, and silver (vapordepositing rate: 0.1 nm/s) and magnesium (vapor depositing rate: 0.8nm/s) are simultaneously vapor-deposited to form the cathode 60.

The EL element of the blue emission/color changing type is thuscompleted through the aforementioned steps.

According to this embodiment, it is possible to form color changingmedia without the use of a lithographic process, and hence to reduce themanufacturing cost of an EL element provided with color changing media.Because it is not necessary to impart photosensitivity to the colorchanging media, there is available an advantage of having a wider rangeof material selection. Since the color changing media is formed bydischarge color changing media precursor by the use of a liquid dropdischarge head, the doping ration of the constituents of the colorchanging media precursor can be appropriately adjusted on the spot. Thisfacilitates adjustment of the pigment constituents of the color changingmedia. This embodiment is applicable also to a white emission/colorchanging type EL element.

Second Embodiment

The structure of an EL element and the manufacturing method thereof ofthe second embodiment will now be described with reference to FIGS.2(A)-3(F).

(Structure of EL Element)

The structure of the EL element will be described with reference to FIG.3(F). This EL element is of the blue emission/color changing type. Amatrix-shaped partitioning member 20 is formed on a glass substrate 10and partitions pixel regions (light-transmission regions) for theformation of color changing media 40A and 40B. By appropriatelyselecting a material for the partitioning member 20, the member cansimultaneously serve to shield light. The color changing media 40A isred color changing media, and the color changing media 40B is greencolor changing media. An anode 30 which may consist of ITO is formed ineach of the pixel regions. By applying a voltage between the anode andthe cathode 60, electrons injected from the cathode 60 encounter thehole injected from the anode 30 in the organic substance (light emittinglayer), thus forming an exciton which is a hole-electron pair. A blueelectroluminescence is obtained from emitting re-combination of thisexciton. R, G and B three primary color light sources (images) areavailable by color-changing this blue light with the color changingmedia 40A for the red pixels, with the color changing media 40B for thegreen pixels, and the direct use of the blue light from the lightemitting layer 50 for the blue pixels. While the blue color changingmedia is not used as color changing media but a blue emission isdirectly used in FIGS. 3(D)-(F), blue color changing media may beprovided when a necessary blue light is not available from emission fromthe blue emitting layer.

(Manufacturing Process of EL Element)

The manufacturing process of an EL element of this embodiment will bedescribed with reference to FIGS. 2(A)-3(F).

Anode Forming Process (FIG. 2(A))

An anode 30 is formed on the substrate 10. For the glass substrate 10,it suffices to use one similar to that in first embodiment. The materialfor the anode should be a light-transmissive conductive material such asITO, or a composite oxide of indium oxide and zinc oxide. In thisprocess, ITO is formed by sputtering into a film having a thickness of0.15 mm, and patterned by a lithographic process into a shapecorresponding to the pixel region.

Partitioning Member Forming Process (FIG. 2(B))

A partitioning member 20 which partition anodes and has an opening tothe pixel region is formed. Various chemical compositions are applicablefor the partitioning member 20. In this embodiment, the descriptioncovers a case where the partitioning member 20 having a light-shieldingproperty serves as a black matrix. The partitioning member 20 may bemade of any material appropriately selected so far as it has asatisfactory durability. More specifically, applicable materials includea negative type resin black made by Fuji Hunt Co., a resist HRB-#01 forhigh-insulation black matrix made by Toppan Printing Co., and a resinblack made by Nihon Gosei Gomu Co., and other black resins dissolved inan organic solvent. These resins are formed into a film having aprescribed thickness of 0.5 to 2.5 mm by the spin coat method, thedipping method, the spray coat method, the roll coat method, or the barcoat method.

Apart from these resins, applicable materials include resin blacksprepared by dispersing metal chromium, carbon or titanium in aphotoresist, and a double-layer structure of nickel, chromium andchromium oxide. In this case, a partitioning member 20 is formed bysputtering or vapor deposition. Then, a resist (not shown) is coatedonto the partitioning, and exposed and developed into a desired pattern.With this resist as a mask, the partitioning member 20 is etched. Thepartitioning member 20 partitioning into a matrix shape is formedthrough these processes. The partitioning member 20 is provided withopenings 21 a to 21 c formed in agreement with positions of the pixelregions.

The partitioning member 20 may be formed by the printing method. In thiscase, it suffices to directly coat the organic material in a matrixshape by the use of relief, intaglio or flat typesetting.

Color Changing Media Precursor Discharge Process (FIG. 2(C))

This is a process of discharging the liquid color changing mediaprecursor to the openings 21 a to 21 c through the liquid drop dischargehead 2. FIG. 2(C) illustrates the red color changing media precursor 40a being discharged to the opening 21 a. In this embodiment, in which thecolor changing media precursor is to be discharged onto the anode 30, aconductive material is used for the color changing media precursor. Morespecifically, the red color changing media precursor may have a chemicalcomposition prepared by mixing a transparent conductive material with acyanine-based pigment, a pyridine-based pigment, a xanthene-basedpigment, or an oxadine-based pigment; the green color changing mediaprecursor may have a chemical composition prepared by mixing atransparent conductive material with a stilbene-based compound and acoumarin-based compound.

When using the blue color changing media, the precursor may have achemical composition prepared by mixing a transparent conductivematerial with a coumarin pigment. Applicable transparent conductivematerials include an ITO alkoxyd solution, a xylene dispersed solutionof ITO particles, and a toluene dispersed solution of a composite oxideparticles of indium oxide and zinc oxide.

When the blue light of the blue emitting layer sufficiently satisfiesthe demand, however, the discharge process of the blue color changingmedia precursor is not necessary.

Color Changing Media Precursor Solidification Process (FIG. 3(D))

This is a process solidifying the color changing media precursordischarged into the openings 21 a and 21 b through a heating treatment.This process causes evaporation of the solvent constituents, and givescolor changing media 40A and 40B.

Blue Emitting Layer Forming Process (FIG. 3(E))

This is a process of forming a blue emitting layer 50 so as to cover thecolor changing media 40A and 40B. As light emitting materials for anorganic EL, there are available pigment molecules which are lowmolecules and conductive polymers which are conjugated polymers. Anorganic thin film can be formed from a low-molecule material mainly byvapor deposition, and from a polymer material, by spin coat method.Although not shown in FIG. 3(E), a double-hetero structure may be formedby forming a hole transfer layer and an electron transfer layer with theblue emitting layer in between. The film forming method in detail is thesame as in first embodiment.

Cathode Forming Process (FIG. 3(F))

As cathode 60 is formed on the blue emitting layer 50. Preferablematerials for the cathode include alkaline metals and alkali earthmetals, such as Mg/Ag and Al/Li alloys. The film forming method indetail is the same as in first embodiment. Upon forming the cathode 60,the blue emission/color changing type EL element is completed.

The EL element manufactured in this embodiment has a structure in which,particularly as shown in FIG. 3(F), a layer formed by a dischargingmethod with the used of the liquid drop discharge head between the anodeand the cathode (i.e., color changing media) and a layer formed bycoating or vapor deposition (i.e., the blue emitting layer) arelaminated for some pixels (for example, the red pixels and the greenpixels), and as required, a layer formed by the discharging method isnot provided between the anode and the cathode, but only a layer formedby coating or vapor deposition (i.e., the blue emitting layer) isprovided for some other pixels (for example, the blue pixels).

According to this embodiment, in which the color changing media itselfis conductive, it is possible to provide an EL element having colorchanging media located between the anode and the blue emitting layer.Because color changing media can be formed without using a lithographicprocess, the manufacturing cost of EL element can be reduced. Absence ofthe necessity to impart photosensitivity to the color changing mediaprovides an advantage of a wider range of material selection. Since thecolor changing media is formed by discharging the color changing mediaprecursor by the use of the liquid discharge head, it is possible toappropriately adjust the doping ration of the constituents of the colorchanging media precursor on the spot, thus facilitating adjustment ofthe pigment constituents of the color changing media.

Third Embodiment

The structure of an EL element and the manufacturing method of the thirdembodiment thereof will be described with reference to FIGS. 1(A)-(C).

(Structure of EL Element)

The structure of the EL element will be described with reference to FIG.4(C). In this EL element, a partitioning member 70 which may consist ofa resist partitions individual pixel regions, and an anode 30 formed onthe entire surface of a substrate 10, serves as a common electrode. Forexample, red color changing media 40A, a blue emitting layer 50 and acathode 60 are sequentially laminated in the red pixel region.

(Manufacturing Process of EL Element)

The manufacturing process of the EL element will be described withreference to FIGS. 4(A)-(C). As the anode 30, a resist 70 is spin-coatedon the glass substrate 10 having an ITO film formed on the surfacethereof (FIG. 4(A)). The resist 70 is patterned in accordance with thepixel region and openings 71 a to 71 c are formed (FIG. 4(B)). The colorchanging media precursor is discharged into the openings 71 a and 71 bthrough a liquid drop discharge head, and the discharged color changingmedia precursor is solidified to form color changing media 40A and 40B.Then, a blue emitting layer 50 and a cathode 60 are formed in theopenings 71 a to 71 c. In this case, the color changing media precursorshould be conductive. Specifically, it suffices to use the sameconstituents (materials) as in the second embodiment.

According to this embodiment, the resist 70 plays the role ofelectrically insulating the individual cathodes 60. Because it ispossible to pattern the cathode 60 in agreement with the pixel regionwithout using a lithographic process or an etching process, themanufacturing process can be simplified, thus permitting reduction ofthe manufacturing cost.

Fourth Embodiment

The structure of an EL element and the manufacturing method thereof willbe described with reference to FIGS. 5(A)-(D).

(Structure of EL Element)

The structure of the EL element will be described with reference to FIG.5(D). This EL element is an improvement over that of the thirdembodiment. An insulating film 80 is formed on the lower part of thepartitioning member 70. This insulating film 80 serves to cut leakcurrent between the cathode 60 and the anode 30 to preventshort-circuiting of the element. This improves the reliability of the ELelement.

(Manufacturing Process of EL Element)

The manufacturing process of the EL element will be described withreference to FIGS. 5(A)-(D). An oxide film 80 is formed as an anode 30on a substrate 10 having an ITO thin film formed on the surface thereof.There is no particular limitation on the kind of the oxide film 80 sofar as it is an insulating thin film: it may be a silicon diode film, azirconium oxide film, a tantalum oxide film, a silicon nitride film, oran aluminum oxide film. The insulating film 80 is patterned so as tomatch with the pixel regions to form openings 81 a to 81 c (FIG. 5(A)).A resist 70 is spin-coated over the entire surface of the substrate 10(FIG. 5(B)). This resist 70 is patterned in accordance wit theinsulating film 80 to leave the resist 70 only on the insulating film 80(FIG. 5(C)). A color changing media precursor is discharged into theopenings 81 a and 81 b through a liquid drop discharge head, andsolidified to form color changing media 40A and 40B. Then, a blueemitting layer 50 and a cathode 60 are sequentially formed in theopenings 81 a to 81 c (FIG. 5(D)). In this case also, the color changingmedia precursor should be conductive. More specifically, it suffices touse the same constituents as in second embodiment.

According to this embodiment, the insulating film 80 cuts leakagecurrent between the cathode 60 and the anode 30, thus serving to preventshort-circuiting of the element. This improves the reliability of the ELelement. Patterning the resist 70 into a wider narrower than the widthof the oxide film 80 structurally improves insulation between the anode30 and the cathode 60, and is more effective for the prevention ofshort-circuiting.

According to the present invention, as described above in detail, inwhich color changing media can be formed without using a lithographicprocess, it is possible to reduce the manufacturing cost of theelectroluminescence element. Because it is not necessary to impartphotosensitivity to the color changing media, there is available a widerrange of material selection. Further, since the color changing mediaprecursor is discharged through the liquid drop discharge head andsolidified to obtain color changing media, it is possible to easilyadjust the doping ration of constituents of the color changing mediaprecursor on the spot to a value the most suitable for color changingproperties.

What is claimed is:
 1. A manufacturing method of an electroluminescenceelement comprising: forming partitioning members having a plurality ofpixel openings so as to correspond to pixel regions of theelectroluminescence element; discharging a fluid including a colorchanging constituent toward each of said openings with a liquid dropdischarge head; solidifying the fluid to form a color changing media ineach of the plurality of pixel openings; and forming a light emittinglayer that causes a light, a wavelength of the light being converted bythe color changing media; wherein the color changing media and the lightemitting layer are formed independently from each other.
 2. Themanufacturing method of an electroluminescence element according toclaim 1, discharging the fluid including the color changing constituentcomprising discharging the fluid while adjusting a doping ratio of thecolor changing constituent of the fluid.
 3. The manufacturing method ofan electroluminescence element according to claim 1, said color changingconstituent being selected from a group consisting of red color changingconstituent, green color changing constituent and blue color changingconstituent.
 4. The manufacturing method of an electroluminescenceelement according to claim 3, the red color changing constituent havinga chemical composition comprising one of a cyanine-based pigment, apyridine-based pigment, a xanthene-based pigment, and an oxadine-basedpigment.
 5. The manufacturing method of an electroluminescence elementaccording to claim 3, the red color changing constituent having achemical composition prepared by dispersing (a) a rhodamine-basedfluorescent pigment, and (b) a fluorescent pigment which absorbs rays ina blue region and induces energy transfer or re-absorption to saidrhodamine-based fluorescent pigment into a light transmitting medium. 6.The manufacturing method of an electroluminescence element according toclaim 3, the green color changing constituent having a chemicalcomposition comprising a stilbene-based compound and a coumarin-basedcompound.
 7. The manufacturing method of an electroluminescence elementaccording to claim 3, the blue color changing constituent having achemical composition comprising a coumarin pigment.
 8. The manufacturingmethod of an electroluminescence element according to claim 1, furthercomprising after forming the color changing media, forming a lightemitting layer by coating or by vapor deposition on an upper side of thecolor changing media.
 9. A manufacturing method of anelectroluminescence element comprising: forming a plurality of anodes;forming a plurality of partitioning members, said partitioning membersforming a plurality of pixel openings above said anodes; discharging afluid including a color changing constituent toward each of saidplurality of pixel openings with a liquid drop discharge head to coversaid anodes with said fluid; solidifying the fluid to form a colorchanging media in the openings; disposing a light emitting layer thatcauses a light to be emitted, a wavelength of the light being convertedby the color changing media; and disposing a cathode over said lightemitting layer; wherein the color changing media and light emittinglayer are formed independently from each other.
 10. The manufacturingmethod of an electroluminescence element according to claim 9,discharging the fluid including the color changing constituentcomprising discharging the fluid while adjusting a doping ratio of thecolor changing constituent of the fluid.
 11. The manufacturing method ofan electroluminescence element according to claim 9, said color changingconstituent being conductive and being a color changing constituentselected from a group consisting of red color changing constituent,green color changing constituent and blue color changing constituent.12. The manufacturing method of an electroluminescence element accordingto claim 9, further comprising after forming the color changing media,forming a light emitting layer by coating or by vapor deposition on anupper side of the color changing media.
 13. The manufacturing method ofan electroluminescence element according to claim 9, a contact anglebetween a material composing a nozzle surface of said liquid dropdischarge head and the fluid including the color changing constituentbeing within a range from 30 to 170 deg.
 14. The manufacturing method ofan electroluminescence element according to claim 9, the fluid includingthe color changing constituent having a viscosity within a range from 1to 20 mPas.
 15. The manufacturing method of an electroluminescenceelement according to claim 1, the fluid including the color changingconstituent having a surface tension within a range from 20 to 70dynes/cm.
 16. The manufacturing method of an electroluminescence elementaccording to claim 1, said liquid drop discharge head comprising apressurizing chamber substrate having a pressurizing chamber whichstores said fluid including the color changing constituent and apiezo-electric thin film element attached to a position permittingapplication of a pressure to said pressurizing chamber.
 17. Anelectroluminescence element comprising: a light emitting layer thatemits light; an anode and cathode arranged with said light emittinglayer in between to form a pixel region; partitioning members having aplurality of pixel openings at a position to which said pixel regioncorresponds; a color changing media, discharged and solidified in eachof said plurality of openings, for wavelength-converting light emittedfrom said light emitting layer wherein the color changing media and thelight emitting layer are independently positioned, the color changingmedia being positioned between the anode and the cathode, and the colorchanging media being positioned so as to convert the wavelength of lightfrom the light emitting layer.
 18. The electroluminescence elementaccording to claim 17, said electroluminescence element having alamination structure comprising the cathode, the light emitting layer,the color changing media and the anode.
 19. The electroluminescenceelement according to claim 17, said color changing media beingconductive and being color changing media selected from a groupconsisting of red color changing media, green color changing media andblue color changing media.